Oilfield fluids (e.g., oil, gas, and water) generally comprise complex mixtures of aliphatic hydrocarbons, aromatics hydrocarbons, heteroatomic molecules, anionic and cationic salts, acids, sands, silts, and clays. Other materials also may be contained in oilfield fluids.
Oilfield fluids, when subjected to severe conditions, comprising heat, pressure, and turbulence, during retrieval, often lead to scale formation, salt formation, paraffin deposition, emulsification (both water-in-oil and oil-in-water), gas hydrate formation, corrosion, asphaltene precipitation, and paraffin formation within oil and/or gas production wells and on the surfaces of equipment external to the subterranean formations.
Scale and other deposits typically decrease permeability of, and therefore conductivity within, the subterranean formation, reducing well productivity and shortening the lifetime of production equipment.
Well treatment agents are often used in production wells to prevent the deleterious effects caused by such formations and precipitates. For instance, scaling in the formation and/or in the production lines downhole and at the surface is often controlled by the use of scale inhibitors.
At the present, in order to clean scales from wells and equipment, typically it is necessary to stop production to add treatment agents, which is both time-consuming and costly.
For instance, scaling in the formation and/or in the production lines downhole and at the surface may be controlled by the use of scale inhibitors.
One approach has been to continuously inject well treating agents. For example, see U.S. Pat. No. 8,343,897. This method teaches that the treatment be made after stimulation or hydraulic fracturing has concluded, or that production to be stopped while the treating agents are introduced.
U.S. Pat. No. 7,493,955, discloses a method of introducing well treatment additives adsorbed on activated carbon, silica particulates, precipitated silica, zeolite, diatomaceous earth, ground walnut shells, fuller's earth and organic synthetic high molecular weight polymers. However, these insoluble absorbents remain in the formation after the treatment within the proppant pack or the fracture after all the well treatment agents have been released from the absorbent, thereby causing a reduction in permeability and conductivity within subterranean formations.
US Patent Application No. 2006166838 discloses a method for the preparation of microparticles for treating hydrocarbon bearing formations wherein a well treatment agent is enclosed on the polymer carrier, which degrades to allow the treatment agents to be released.
Patent Application No. WO2016003304 discloses a composite proppant wherein a solid proppant is contained within a polymeric carrier. When the polymer degrades a solid proppant remains, which may reduce the permeability and conductivity within subterranean formations.
US Patent Application No. 2004115378 discloses a delivery system for a controlled release of downhole additives wherein the additive is enclosed within a water dispersible container. This system depends on large porous particles that allow the agents to permeate through the pores.
US Patent Application No. 2004043906 discloses use of a polymeric material that is permeable and forms a matrix of polymer to encapsulate the treatment agents. This invention teaches that the treatment agents are desorbed from the matrix. After all the treatment agent is exhausted from the polymer matrix, the polymer shell remains and will reduce the conductivity.
US Patent Application No. 2016075941 discloses the use of a mixture of porous and nonporous proppant compositions. The non-degradable proppant is encapsulated within the degradable polymeric shell. The useful of such a product depends on the degradation or hydrolysis rate of the polymer which is uncontrollable as it depends on the subterranean conditions. After all the treatment agent is exhausted from the outer shell of the proppant, the inner insoluble shell remains and will reduce the conductivity.
U.S. Pat. No. 3,305,019 discloses a composition for stimulating gas production.
No composite or method has been found that is capable of a controlled release of treating agents under harsh conditions without leaving insoluble materials within the subterranean formations, thereby reducing conductivity within the formation.
Thus, there is a need for a method that provides a controlled slow release of well treating chemical without stopping production from the well and that does not leave unwanted detrimental materials in the well that reduce conduction.